What is a Power Diode?

A power diode is a semiconductor device that is designed to handle high voltage and high current levels than a conventional signal diode. It consists of two terminals such as anode & cathode and conducts current in only one direction. The operating principle of a power diode is the same as that of the conventional diode, but it differs in its basic structure.

A conventional diode has a PN junction, which is formed by joining n-type and p-type semiconductor materials. Whereas the construction of a power diode includes three layers like the P+ layer, n– layer, and n+ layer. The P+ layer is heavily doped and acts as an anode. The middle layer is the n– layer which is lightly doped. The last layer is the n+ layer which is heavily doped and acts as the cathode. The width of the middle layer decides the breakdown voltage of the power diode.

These constructional differences make the power diodes ideal for use in HF welding, power converters, switched-mode power supplies, power factor correction diode, protection purposes, uninterrupted power supply, AC/DC converter, DC/DC converter, secondary rectification, auxiliary power supply, freewheeling function, reverse battery protection, and LED lighting applications. 

Types of power diodes:

Based on the reverse recovery time as well as the process of manufacturing, power diodes are classified into three types- fast recovery diode, Schottky power diodes, and general-purpose diodes.

Based on applications, power diodes are classified as rectifier diode, freewheeling diode, protection diode, and silicon diode.

Fast Recovery Diode: The recovery time is the finite amount of time taken by a diode to discharge (during conducting state, it stored the charges) when switching from the conducting to the blocking state.

Schottky Power Diode: It is a type of semiconductor diode formed by a metal-semiconductor (n-type silicon) junction. Schottky power diodes offer a very fast switching speed and low forward voltage drop. Hence, it is ideal for use in high-frequency switching power supplies and instrumentation applications.

General Purpose Diode: These diodes are suitable for low frequency & low-speed applications such as UPS, battery chargers, welding, and traction.

Rectifier Diode: It is a type of power diode that is used for rectification (AC to DC conversion) applications.

Freewheeling Diode: It is a type of power diode that is connected across an inductive load to prevent a sudden voltage spike. Voltage spike occurs across an inductive load due to interruption of supply current or sudden reduction.

Protection Diode: It is a type of power diode that is used for the protection purpose of a device. These diodes are ideal for use in ESD protection of signals in HDTV, server interconnects, PC monitors, and peripherals.

Silicon Diode: It is a type of power diode that is made up of silicon semiconducting material. Silicon diode offers benefits like low forward voltage, low reverse recovery charge, and low reverse recovery current. These diodes are ideal for use in motor control and drives, air conditioning, general-purpose drives (GPD), and industrial SMPS applications.

Key Specifications of Power Diodes:

Configuration of Diode: The power diodes are available with different configurations such as a single diode, dual diode, triple diode, quad diode, etc.

Forward Current: It refers to the current that flows from anode to cathode during the forward bias condition and is expressed in Ampere (A).

Forward Voltage: It represents the voltage drop across anode and cathode terminal when the diode is in ON state or forward bias condition. It is expressed in volts (V).

Reverse Current: is defined as the current that flows in the opposite direction when a diode is reverse biased.

Reverse Voltage: It represents the voltage drop across the diode terminals (anode and cathode) when the diode is in a reverse bias state. It is expressed in volts (V).

Repetitive Peak Reverse Voltage: It represents the maximum allowable value of reverse voltage that can be repeatedly applied to the reverse direction of the diode. It is expressed in volts (V).

Non-Repetitive Peak Forward Current: It represents the maximum surge current that a diode can handle. Surge current is the current flow through a device at a short duration and has a magnitude more than the rated value current.

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